Ruler



FIG. 1 is a top, front and left side perspective view of a ruler showing my new design;

FIG. 2 is a top, rear and right side perspective view thereof; and,

FIG. 3 is a top plan view thereof.

The broken lines in the drawings illustrate portions of the ruler which form no part of the claimed design. 

CLAIM The ornamental design for a ruler, as shown and described. 